Costas loops such as that described in U.S. Pat. No. 3,101,448 have typically been used as tracking loops in suppressed carrier data demodulation systems. However, tracking loops such as the Costas loop do not provide fast initial carrier acquisition since narrow loop bandwidths are used in such systems to maintain lock and minimize phase jitter in noisy environments. This problem may be alleviated to some degree by utilizing dual bandwidth tracking loops where a relatively wide bandwidth is used for fast initial carrier acquisition and a relatively narrow bandwidth is utilized once the tracking loop has adequately locked to the carrier. Tradeoffs in the design of such dual bandwidth tracking loops are discussed in the book "Synchronization Systems In Communication and Control", by William C. Lindsey and published by Prentice Hall, 1972, in Chapter 5. However, in order to practically utilize a dual bandwidth tracking loop, a loop-lock detector must be utilized to control the bandwidth switching. A loop-lock detector that is suitable for use with a Costas loop is described in the book "Spread Spectrum Systems", by Dixson and published by Prentice Hall, 1972, in Chapter 5 at pages 156-158. The loop-lock detector presented by Dixson utilizes three multipliers and two low pass filters. However, the loop lock indicator does not insure relatively fast acquisition times for large frequency offsets when receiving weak carrier signals.